10.1021/jo951194h.s001
David Crich
David
Crich
Sanxing Sun
Sanxing
Sun
Jarmila Brunckova
Jarmila
Brunckova
Chemistry of 1-Alkoxy-1-glycosyl Radicals: The Manno- and
Rhamnopyranosyl Series. Inversion of α- to β-Pyranosides and the
Fragmentation of Anomeric Radicals
American Chemical Society
1996
Photochemical conditions
Fragmentation
Anomeric Radicals
Rhamnopyranosyl Series
series
abstraction
stereoselective quenching
side reactions
formation
1996-01-26 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Chemistry_of_1-Alkoxy-1-glycosyl_Radicals_The_Manno-_and_Rhamnopyranosyl_Series_Inversion_of_-_to_-Pyranosides_and_the_Fragmentation_of_Anomeric_Radicals/3700824
The formation and stereoselective quenching of 1-mannopyranosyl
radicals by a tributyltin hydride-mediated intramolecular 1,5-hydrogen abstraction sequence is described.
A competing process is
1,4-hydrogen atom abstraction leading principally to
glucopyran-2-ulosides. Fragmentation of the
anomeric radical resulting in the formation of ring opened products is
a problem in certain series.
The chemistry is dictated to a considerable extent by the nature
of the protecting groups employed
with the 4,6-benzylidene series and, for rhamnose, the Ley
3,4-dispiroketal, being particularly
susceptible to the 1,4-hydrogen atom abstraction but less to the
fragmentation. Photochemical
conditions are described, in which these side reactions are practically
eliminated, and applied to
the inversion of an α- to a β-mannoside in a
disaccharide.